The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Automatic fire protection sprinkler systems are used to protect property and life from damage and loss due to fires. The types of systems that are currently used for residential fire protection are wet systems that include pressurized liquid throughout the piping system using a system check valve and flow alarm. These systems operate when a sprinkler opens due to heat activation of a fusable heat activated link or glass bulb of the sprinkler allows the release of a plug that permits the flow of liquid or fire suppressant until the sprinkler system is manually shut off. Another type of system is a preaction system that includes supervision of discharge system integrity using air, and are typically designed for industrial or commercial applications. The systems designed for industrial or commercial applications are unnecessarily complicated and more costly for residential fire protection. The sprinklers used in residential sprinkler applications are typically evaluated and listed for wet applications only, meaning that the system piping is full of fire suppressant up to the sprinkler head. The industrial and commercial applications require more constraints as required by code and are more demanding on the design. Also, the use of lower cost PVC pipe typical of use in residential sprinkler systems is prohibited for use on air-supervised dry preaction sprinkler systems, unless specific approvals have been obtained from third party laboratory agencies. Constraints that the fire protection codes demand require trained personnel in the field of fire protection to service the existing systems. The designs are more robust for industrial applications due to many factors such as higher system pressure due to bigger supply pumps, to delay in liquid discharge due to replacement of air in the piping system with liquid which requires a substantial amount of time delay.
Wet sprinkler systems are widely used as a cost effective means for residential fire protection systems. Home owners, however, are largely concerned about liquid damage due to accidental discharge of the fire suppressant. Fire suppressant may exit the wet system for many reasons. A pipe could freeze and break, a person could accidentally set off a sprinkler head mechanically, a pin-hole leak may develop in the piping system, or the piping system or sprinkler heads may be otherwise damaged in other ways. The end user is typically concerned about the unintended discharge of fire suppressant liquid while they may be in the dwelling, but more so if they are not within the dwelling for a length of time. Though notification appliances exist, it is still desirable in the art to provide means to address the potential for liquid damage that can occur due to the inadvertent discharge of fire suppressant liquid.
Residential fire sprinkler systems are supplied with liquid from either a municipal water supply main or a local reservoir and pump system separated from the domestic liquid supply system. The sprinkler system is required to include a main supply pipe with liquid flow alarm. The main supply extends up or down to a series of branch pipes that are evenly spaced throughout the protected structure. Dry preaction systems currently exist in which the sprinkler piping network is provided with an air volume that must be depleted before the liquid will discharge from the sprinkler head that has been activated. For large buildings and multiple floor structures, the distance from the typical preaction system control valves can be large, including large volumes of air. If future modifications to the structure are made, and additional sprinklers are added, this can greatly affect the results of the dry system's performance. Also, in addition to the liquid supply system, an air maintenance system is also required to provide supervision of the piping system integrity. The benefit of a dry preaction system is that because the piping network is free from water, the risk of pipe freezing is eliminated. However, the complexity of maintaining the air maintenance system significantly increases the cost of the system. Furthermore, the inadvertent breaking of a sprinkler head would typically trigger activation of the control valve allowing the release of full flow of fluid through the piping system.
In the fire protection sprinkler industry, wet systems utilize a flow switch and check valve combination to provide an alarm to indicate when a flow condition is present. With a typical wet system, that includes a check valve style valve wherein liquid pressure in the system holds the check valve closed until an open device in the piping system, such as a fused sprinkler, opens allowing liquid to flow. The check valve will open allowing full system pressure and liquid flow to enter the piping system and discharge from the piping and sprinklers. Typical preaction systems currently available that use a flow control valve held closed by system supply liquid pressure require air supervision of the system piping and additional air pressure maintenance systems. Accordingly, it is desirable in the art to provide a less complex fire suppressant sprinkler system that is capable of providing immediate protection of a protected area but provides effective limitations on the amount of fire suppressant liquid inadvertently discharged from the sprinkler system.